With rapid development of the Internet and Optical Fiber Technologies, the integration of Internet Protocol (IP) technology and Optical Network technology would be a considerable tendency of the network development in the future. The Generalized Multi-Protocol Label Switching (GMPLS) technology, which inherits almost all the properties and protocols of Multi-Protocol Label Switching (MPLS) technology, provides a beneficial way to integrate the IP layer and the Optical layer. Being an extending application of MPLS in the Optical Network, the GMPLS could manage networks constructed through different technologies using a unified control plane, and provide an important guarantee for simplifying network structure, reducing network administration cost and optimizing network performance. To meet the future requirements of dynamically providing network resources and transmitting signalings in an ASON, it is necessary to extend and update the traditional MPLS technology. The GMPLS is an extension of MPLS towards the optical network, which not only supports traditional switches, such as packet switch, time division switch, wavelength switch and optical switch, but also modifies and extends original routing and signaling protocols. To support circuit switch and optical switch, the GMPLS employs a special label to identify parameters such as optical fiber, waveband, wavelength and time-slot etc., the length and format of the special label varies with different application environments. For instance, in a wavelength label switching application, the port/wavelength label is of 32 bits, representing the optical fiber or port or wavelength being used. The port/wavelength label does not have fields such as an experimental bit, bottom of the label stack, etc., which is different to a traditional label, while it has local validity only among neighbor nodes which is the same as a traditional label. The value of the label could be manually assigned or dynamically decided by a protocol, thus the label format of GMPLS leaves a lot of space for supporting more intelligent services.
In the prior art, service establishment of ASON is controlled by signalings of GMPLS. The GMPLS protocol suite includes: link management protocol which is used for finding out neighbor nodes; extended Open Shortest Path First (OSPF) protocol and Intermediate System Routing protocol which are used for link state distribution; Constraint-Based Routing Label Distribution Protocol (CR-LDP) and Resource Reservation Protocol-Traffic Engineering (RSVP-TE) which are used for managing and controlling channels. Both the RSVP-TE and the CR-LDP could bear all the objects defined in the GMPLS system, thus the establishing, modifying, inquiring and deleting of Label Switching Path (LSP) are completed by the CR-LDP or the RSVP-TE. Once an LSP is established, the ASON is able to transmit various services over the LSP at a high speed.
The ASON provides 1+1 protection to better protect the transmitted services. The 1+1 protection mechanism is using two different paths (e.g. LSPs) to transmit the primary service and the slave service of a certain service respectively, wherein the primary service and the slave service are completely the same. A detector is configured at the receiving end to select better service data from the two paths. In the following, a service requiring 1+1 protection is called a 1+1 protection service, which includes a primary service and a slave service. For the 1+1 protection service, each path has rerouting ability, that is, if either of the two paths fails, the path could recover from the failure through rerouting.
The GMPLS completes service transmission in the ASON through establishing LSPs. As far as a 1+1 protection service is concerned, LSP IDs generated according to the initial node for indentifying LSPs and identifiers of both the primary service and the slave service could make the two paths of the primary service and the slave service exclusive with each other at the initial manual configuration. The exclusion of paths means there are no other common nodes and/or links in these two paths except for the initial node and/or terminal node.
The process of establishing LSPs for a 1+1 protection service is introduced in the following with reference to FIG. 1.
As shown in FIG. 1, the ASON 1 represents an optical transport network, including node device 10, node device 11, node device 12, node device 13, node device 14, node device 15 and node device 16, with the connection relations configured in advance among these node devices. It should be pointed out that, in FIG. 1, the initial node of the 1+1 protection service is node device 12, and the terminal node is node device 14. Since both of the two nodes are inside the ASON 1, node device 12 is also the entrance node of the ASON 1, and node device 14 is the exit node of the ASON 1.
In the process, a link between node devices 12 and 10 is first established at Step 110, and a link between node devices 10 and 11 is established at Step 120. Then, a link between node devices 11 and 14 is established at Step 130. After that, an LSP including the links established at Steps 110, 120 and 130 in the ASON 1 is formed to be a protection path for transmitting the slave service of the 1+1 protection service.
At Step 140, a link between node devices 12 and 13 is established, and at Step 150, a link between node devices 13 and 14 is established. After that, an LSP including the links established at Steps 140 and 150 in the ASON 1 is formed to be a working path for transmitting the primary service of the 1+1 protection service.
When the protection path established at Steps 110, 120 and 130 works well, the protection path performs 1+1 protect for the working path established at Steps 140 and 150. In FIG. 1, after a certain 1+1 protection service transmitted through the ASON 1 arrives at node device 12, service data of the 1+1 protection service is not only transmitted through the working path established at Steps 140 and 150, which means the service data can arrive at node device 14 through node devices 12 and 13, but also copied by node device 12 to the protection path established at Steps 110, 120 and 130 for transmission, which means the same service data can arrive at node device 14 through node devices 12, 10 and 11. Then, the detector on node device 14 may choose better service data from these two LSPs. Normally, the service data transmitted through node devices 12 and 13 will be selected. It can be seen that the above process enhances the reliability of service data transmission.
Moreover, in the 1+1 protection service, it is specified that the working path and the protection path do not have any other intersection except for the entrance node and the exit node, that is, no other nodes and/or links of these two paths are the same. Therefore, although there is a physical channel between node devices 10 and 13, they could not be included together in any LSP.
The situation when the protection path established at Steps 110, 120 and 130 goes wrong will be depicted hereinafter.
As shown in FIG. 1, assuming the link established at Step 120 is broken, the protection path established through Steps 110, 120 and 130 could not work any more. In this case, if 1+1 protection is still desired by the services passing through the ASON 1, a new protection path should immediately be found and established within the ASON 1. That is to say, node device 12 may conduct rerouting after receiving a failure notice from node device 10, and calculate a new protection path according to network topology information of the ASON 1.
Then, a link between node devices 12 and 15 is established at Step 160, and a link between node devices 15 and 16 is established in succession at Step 170, finally a link between node devices 16 and 14 is established at Step 180.
After that, the new protection path is set up between node devices 12, 15, 16 and 14 to replace the old one established through Steps 110, 120 and 130, and provides 1+1 protection for the working path established through Steps 140 and 150.
Moreover, according to the specification of 1+1 protection mechanism, no other intersection is allowed between the working path and the protection path except for the entrance node and/or exit node. Thus, how to guarantee the exclusion between the working path and the new protection path has become a problem.
In addition, when the initial node and/or terminal node of the 1+1 protection service are/is outside the ASON, no corresponding solution is available yet to guarantee the exclusion between the working path and the protection path. The reason lies in that inside the ASON, there is no common entrance node and/or exit node for these two LSPs transmitting the 1+1 protection service, thus the exclusion of LSPs could not be guaranteed according to the ordinary 1+1 protection mechanism. With regard to this problem, no solution has yet been given in standards and drafts of Internet Engineering Task Force (IETF), International Telecommunication Union (ITU) or Optical Interworking Forum (OIF). In other words, when the initial node and/or terminal node of the 1+1 protection service are/is outside the ASON, there is no mature solution in the industry on implementing 1+1 protection for services in the ASON.